-s causes cmp to print nothing for differing files, for use when only
the exit status is of interest.
-z compares the file size first, for regular files, and fails the
comparison early if they do not match.
Prior to this change -s implied -z as an optimization, but this is not
valid when file offsets are specified. Now, enable the -z optimization
for -s only if both skip arguments are not provided / 0.
Note that using -z with differing skip values will currently always
fail. We may want to compare size1 - skip1 with size2 - skip2 instaead,
and in any case the man page should be clarified.
PR: 252542
Fixes: 3e6902efc8
Reported by: William Ahern
Reviewed by: markj
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28071
Split the rights-limiting code into two cases: if one of the input
files isn't a regular file, use caph_limit_stream(3) instead of
open-coding the same logic; if both input files are regular files,
and the initial attempts to map them succeed, we limit the rights on
those files to CAP_MMAP_R.
Add a regression test for PR 234885.
PR: 234885
Reviewed by: delphij
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19216
Test failures don't seem to propagate up if atf_check is run in
a pipeline. Thus, the tests continued to pass despite the bug reverted
in r343245.
MFC after: 1 week
